Mixing 1066 with 1333mhz ram.

Discussion in 'iMac' started by Qwerty11, Nov 9, 2011.

  1. Qwerty11 macrumors regular

    Sep 1, 2010
    My mac has two 2gb 1066mhz sticks in it from the factory. I just got a steal on two 4gb 1333mhz stick. Can I pop these into the other two slots and everything will be copasetic?
  2. Macman45 macrumors G5


    Jul 29, 2011
    Somewhere Back In The Long Ago
    I'm Afraid Not

    You are going to have major issues if you mix the types.....If you want to upgrade you are going to have to buy two more of the faster modules, or replace the older ones with the new ones.
  3. B.A.T macrumors 6502a

    Oct 16, 2009
  4. paulrbeers macrumors 68040

    Dec 17, 2009
    Doubtful. Most likely your mac will just run all the ram at the slowest speed. If you do use to different sizes, you will lose the dual channel memory which will reduce your overall system speed by a few percentage points (as much as 10% in high memory bandwidth applications).

    So yes you should be able to mix them, but it won't run optimally. You are best to use two sticks of the same speed and size.
  5. Mike in Kansas macrumors 6502a

    Mike in Kansas

    Sep 2, 2008
    Metro Kansas City
    I have heard of users putting slower sticks into faster systems (i.e. 1066 sticks into a MB with 1333 RAM speed) but not putting faster sticks into a slower MB RAM slot. You can usually mix RAM as long as the fastest RAM is no faster than the system was designed for, but not about the other way around.
  6. binba macrumors newbie

    Jul 23, 2010
    Uh, the opposite of what everyone said.

    You should be able to mix them fine, but to be more specific - the speed difference is not a problem. You CAN put faster RAM in a slower system, it should scale back to the correct lower speed (whether to match other sticks or the system bus).

    Notice there's a bunch of other potential caveats. All the following parameters need to match:
    • ECC
    • Registration/buffering
    • pin count
    • Voltage

    Google the full part # of your modules and look up the full specs on the manufacturer's website, and compare.

    Shows you what's the problem is with getting advice from online forums.
    Just in case someone stumbles upon this thread (like I did).

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